Re: rotary gap electrodes

In a message dated 96-08-19 00:39:59 EDT, you write:

 I'm asymptotically approaching the state of rotary gap construction known 
 as completion.  I thought I would ask for others input before proceeding.
 The design of my rotary has two 1" thick 14"x14" pieces of plexiglass to 
 hold the bearings and act as side shields.  The stationary electrodes are 
 going to be mounted to the plexiglass and poke into the box where the 
 disc is rotating.  I am using 1/8" tungsten TIG welding rods for 
 stationary electrodes.  The input power will be less than 10KVA.
 My questions are: How much cooling of the stationary electrodes do I 
 need to do?  Will putting the W (tungsten) rod into a piece of 5/8" brass 
 rod 2" long be enough to prevent the rod assembly from getting so hot 
 that it melts the plexiglass?  I have also considered some sort of 
 non-thermoplastic insulator to surround the brass.  Another option is a 
 1" rod of Al with the W rod in it.  The Al could have cooling fins turned 
 on it too if necessary.  I don't figure ohmic heating will be much of a 
 factor, but the arc will be hot and so heat the electrodes.
 Any input would be appreciated.
 Chip >>


I have my stationary tungsten contacts mounted in 1" x 1" copper blocks that
are about 3" high.  These are then mounted in nylon blocks for insulation and
the nylon is mounted to the steel base.  I would say you will need some heat
sinking although I don't know how much.  The ends of the tungsten rods do get
hot enough to melt!

I use 5/16" dia. tungsten because that is what the welding shop had - used
for TIG welding.

Ed Sonderman